Whatif they did ? To me it is one of the great whatif of the space shuttle era (1971 - 2011)
Even suborbital, the X-33 could be used for all kind of military missions. Also, with an expendable uppper stage it could perhaps launch small payloads to Earth orbit. Sounds familiar ? DARPA XS-1 maybe ? https://en.wikipedia.org/wiki/XS-1_(spacecraft)
The X-33 would be notably bigger and faster, than the reusable XS-1 stage 1.